Segmentation of rifts through structural inheritance: Creation of the Davis Strait

Mesozoic‐Cenozoic rifting between Greenland and North America created the Labrador Sea and Baffin Bay, while leaving preserved continental lithosphere in the Davis Strait which lies between them. Inherited crustal structures from a Palaeoproterozoic collision have been hypothesized to account for the tectonic features of this rift system. However, the role of mantle lithosphere heterogeneities in continental suturing has not been fully explored. Our study uses 3‐D numerical models to analyze the role of crustal and sub‐crustal heterogeneities in controlling deformation. We implement continental extension in the presence of mantle lithosphere suture zones and deformed crustal structures and present a suite of models analyzing the role of local inheritance related to the region. In particular, we investigate the respective roles of crust and mantle lithospheric scarring during an evolving stress regime in keeping with plate tectonic reconstructions of the Davis Strait. Numerical simulations, for the first time, can reproduce first order features that resemble the Labrador Sea, Davis Strait, Baffin Bay continental margins and ocean basins. The positioning of a mantle lithosphere suture, hypothesized to exist from ancient orogenic activity, produces a more appropriate tectonic evolution of the region than the previously proposed crustal inheritance. Indeed, the obliquity of the continental mantle suture with respect to extension direction is shown here to be important in the preservation of the Davis Strait. Mantle lithosphere heterogeneities are often overlooked as a control of crustal‐scale deformation. Here, we highlight the sub‐crust as an avenue of exploration in the understanding of rift system evolution

Multiphase Phanerozoic Subsidence and Uplift History Recorded in the Congo Basin: A Complex Successor Basin

International audienceThe Congo Basin of central Africa is a large iconic Phanerozoic sedimentary basin whose origin and tectonic evolution are poorly understood, mostly because of a lack of modern stratigraphic data, reflecting a long hiatus in field investigations during the past five decades. It is usually assumed that the Congo Basin experienced a long and continuous history of slow subsidence since the late Precambrian (e.g. 2–4 m/Ma), linked to steady-state mantle processes. Here, we used revised sedimentological and stratigraphic data of the four historic deep boreholes drilled in the center of the basin to calculate a new first-order model for its subsidence and uplift history. Because the sedimentary sequences of this basin are largely terrestrial, we apply a new backstripping method especially designed for continental domain. The results reveal two main episodes of subsidence: initially rapid subsidence during the Carboniferous-Triassic (10–20 m/Ma), and then slower subsidence during the Jurassic-Cretaceous (5–10 m/Ma), punctuated by several uplifts at 160–180 Ma (e.g. ‘Karoo’), 120–140 Ma (e.g. ‘Paraná-Etendeka’), and again in the Cenozoic, ca. 30–50 Ma (e.g. ‘Ethiopian’). This complex, multiphase subsidence and uplift history of the Congo Basin can be linked to evolving far-field geodynamic processes that first led the formation of Pangea (large-scale compression) during the late Paleozoic, and then to its break-up associated with successive outpourings of Large Igneous Provinces (or hotspot plumes) and the opening of the Indian and South Atlantic Oceans around Africa

Lithospheric foundering and underthrusting imaged beneath Tibet

Long-standing debates exist over the timing and mechanism of uplift of the Tibetan Plateau and, more specifically, over the connection between lithospheric evolution and surface expressions of plateau uplift and volcanism. Here we show a T-shaped high wave speed structure in our new tomographic model beneath South-Central Tibet, interpreted as an upper-mantle remnant from earlier lithospheric foundering. Its spatial correlation with ultrapotassic and adakitic magmatism supports the hypothesis of convective removal of thickened Tibetan lithosphere causing major uplift of Southern Tibet during the Oligocene. Lithospheric foundering induces an asthenospheric drag force, which drives continued underthrusting of the Indian continental lithosphere and shortening and thickening of the Northern Tibetan lithosphere. Surface uplift of Northern Tibet is subject to more recent asthenospheric upwelling and thermal erosion of thickened lithosphere, which is spatially consistent with recent potassic volcanism and an imaged narrow low wave speed zone in the uppermost mantle